Methods of Manufacturing a Semiconductor Device
Methods of manufacturing a semiconductor device and an apparatus for the manufacturing of semiconductor devices are provided. An embodiment regards providing a process which changes the volume of at least one layer of a semiconductor substrate or of at least one layer deposited on the semiconductor substrate, and measuring a change in volume of such at least one layer using fluorescence. In another embodiment, a change in volume of such at least one layer is measured using reflection of electromagnetic waves.
The present inventions generally relates to the manufacturing of semiconductor devices.
BACKGROUNDIn semiconductor manufacturing, a photoresist pattern is produced by imaging a reticle pattern on a photoresist and developing the photoresist. Afterwards, etching is conducted to transfer the photoresist pattern to the underlying layer. These steps are repeated multiple times to produce a multi-layer semiconductor device. Also, a hard mask pattern may be used to structure an underlying layer.
There is a general desire to monitor and control etching and material deposition processes that occur during semiconductor manufacturing. For example, end point detection during etching is required to produce a desired critical dimension (CD).
SUMMARY OF THE INVENTIONOne embodiment provides a method of manufacturing a semiconductor device. At least one structured layer is produced in a semiconductor substrate. During such producing of at least one structured layer, there is provided at least once a process which changes the volume of at least one layer of the semiconductor substrate or of at least one layer deposited on the semiconductor substrate. Such process could be an etching process or a deposition process. It is measured a change in volume of such at least one layer using fluorescence. For example, a signal indicative of the intensity of X-Ray fluorescence may be determined.
In another embodiment, there is also provided during the producing of at least one structured layer in a semiconductor substrate a process which changes the volume of at least one layer of the semiconductor substrate or of at least one layer deposited on the semiconductor substrate. In this embodiment, it is measured a change in volume of such at least one layer using reflection of electromagnetic waves. For example, X-Rays reflected by the substrate are measured and a signal is provided indicative of the intensity of the reflected X-rays.
In another embodiment, there is provided a method of manufacturing a semiconductor device in which there is provided a top first layer of a semiconductor substrate and a second layer of the semiconductor substrate beneath the first layer, the two layers having a different refractive index for X-Ray radiation. The first layer of the semiconductor substrate is etched. During etching, the substrate is irradiated with X-Rays. The X-Rays reflected by the substrate are measured and it is provided a signal indicative of the reflected X-rays. It is determined a change in the signal and an end point of the etching process is associated with the change in the signal. The change in signal is caused by a changed reflectivity when the material of the first layer is at least partly etched away and the X-Rays are then at least partly reflected by the second layer.
In another embodiment, there is provided a method of manufacturing a semiconductor device which comprises a process which etches a top first layer of a semiconductor substrate or produces such layer, wherein a second layer of the semiconductor substrate is located beneath the first layer. The materials of the first and second layers and the angle of incidence of the incident X-Rays are chosen such that total reflection of the incident X-Rays occurs or disappears when at least a part of the first layer has been processed. The occurrence or disappearance of total reflection corresponding to an increase or drop in the intensity of the reflected X-Rays, which corresponds to the end of the etching or layer producing process. The method may be used for end point detection. Accordingly, in this embodiment, the occurrence or disappearance of total reflection of X-Rays is an indication of the completion of a process step.
A further embodiment regards an apparatus for the manufacturing of semiconductor devices. The apparatus comprises means for changing the volume of at least one layer of a semiconductor wafer or of at least one layer deposited on the semiconductor wafer, an X-Ray radiation source, an X-Ray detection device detecting and measuring a signal indicative of the intensity of X-Rays reflected or emitted by fluorescence by the semiconductor wafer, and evaluating means for associating the signal with the course of the change in volume process.
The drawings show different exemplary embodiments and are not to be interpreted to limit the scope of the invention.
The apparatus further comprises an X-ray radiation source 3 and an X-ray detection device 4. In one embodiment, the X-ray radiation source 3 provides at least one incident X-ray beam of a specified spot size. In one embodiment, the X-ray radiation source 3 is adapted to scan at least a top layer of the wafer 2 with the incidence beam. In the embodiment of
It is pointed out that in other embodiments the X-ray radiation source 3 may not be scanning the wafer 2 but, e.g., illuminating the complete wafer 2. Also, embodiments exist in which a sample volume that is representative of the wafer is irradiated only, without irradiating other areas.
The X-ray detection device 4 detects the signal that is reflected or emitted by fluorescence by area 21 of the semiconductor wafer when irradiated with X-rays by the X-ray radiation source 3. The detection device 4 includes evaluating means for associating the signal with a change in volume that is applied to at least one layer of the semiconductor wafer during a process. The evaluating means may also be provided in a separate unit.
The X-ray radiation source 3 and the X-ray detection device 4 are located either inside or outside the etch chamber 1. In one embodiment, they are located inside the etch chamber 1.
It is pointed out that there may be several detection devices and several X-ray sources located at different angles and with different wavelengths. There may also be provided a control system (not shown) that gives feedback to the process during etch or deposition. The system may be used in-situ or ex-situ and may give feedback for etch of the actual or next wafer.
The apparatus shown in
According to
Such fluorescence in one embodiment is X-ray fluorescence. In other embodiments, instead of X-rays, electromagnetic waves of other wavelengths may be used for exciting fluorescence such us UV light.
X-ray fluorescence (XRF) occurs when materials are exposed to high energetic radiation such as X-ray radiation or Gamma-ray radiation. Following ionization, electrons in higher orbitals fall into the lower orbital to fill the hole left behind. In falling, energy is released in the form of a photon. This so-called fluorescence radiation is characteristic for the atoms present. Further, the fluorescence intensity is directly related to the amount of each material in a given sample.
In the embodiment of
Alternatively, measurements are made at other or additional times between start and end of a process that leads to a change in volume. Also, measurements may be taken essentially continuously to allow endpoint detection.
According to
The sensitivity of this method will be dependent on the ratio between the depth up to which a volume change is introduced into the sample and the depth from which fluorescence radiation can be collected and evaluated (in the following referred to as information depth). The lower this ratio, the higher the sensitivity.
The information depth may be customized by using grazing incidence primary X-ray radiation.
More particularly, in
X-rays from source 3 are radiated on the sample 22. The signal detected by detector system 4 is formed by fluorescence signals from material A of layer 221 and material B of layer 222. However, the collected fluorescence signal comes mainly from the upper layer 221 of etched structures, particularly, before the etching of the top layer 221 has been completed. The penetration depth of the primary X-rays of source 3 may be tuned by varying the angle of incidence α.
As more and more material A is etched away during etching, the fluorescence signal of layer 221 is reduced, until a minimum is reached. Further, eventually, an additional fluorescence signal from material B of layer 222 becomes stronger in the course of the etching process. By determining the minimum of the fluorescence signal from material A and/or determining the fluorescence signal of material B, the course of the etching process can be followed. This can be used, for example, for endpoint detection of the etching process.
Similar remarks apply in case a layer of material is deposited. With increased deposition, the fluorescence signal of the deposited material increases.
According to the described method, direct measurement of volume or mass change is possible. The volume change can be obtained locally as the fluorescence signal can be restricted to a sample volume which is defined by the spot size of the XRF times the information depth of the fluorescence radiation. As the X-ray radiation is local, the fluorescence signal is also local and this way a spatial resolution of the signal is naturally provided for.
According to
In all of the structures shown in
In the following, a further embodiment of a method for manufacturing a semiconductor device using X-ray fluorescence to measure a change in volume of at least one substrate layer is discussed. This method has already been indicated with respect to
In this embodiment, other than in the embodiment previously described with respect to
In such embodiment, the fluorescence signal of the second layer 222 may be evaluated to determine the end point of the change in volume process. For example, if a change in volume process is an etching process such as in
According to this embodiment, a fluorescence signal is detected which is representative of an open area of a substrate layer which is beneath the substrate layer that has been subject to an etching or other process. The intensity of the emission from the layer below the etched layer is a measure of the open area and, therefore, a measure of the etched critical dimension at the measuring spot.
Such measurement may be made for sample volumes by scanning an incident X-ray beam over the wafer as discussed before. Also, one averaging measurement for the complete wafer may be carried out.
In an embodiment, such open area fluorescence signal measurement is implemented for a spacer etch in the course of a double patterning process, for example below 40 nm half-pitch. With a spacer etch, the direction of the incident X-rays in one embodiment is parallel to the respective lines.
With spacer etches, if the etch is too long, the spacer becomes too small, if it is too short, the spacer becomes too wide. Further, there is usually a non-uniformity over the wafer and the shape of the spacer can vary. Therefore, exact control during etch is required to provide for a desired critical dimension (CD). A measurement as discussed above provides end point detection that allows to control such etch. The integrated intensity over a defined dose and defined pattern is sufficiently precise to calibrate a critical dimension versus signal curve for, e.g., a sub-40 nm patterning, especially for sublithographic patterning techniques.
In one embodiment, this method provides for a kind of “0-1” transition, the “1-signal” occurring when the top layer has been partially etched through such that the fluorescence signal of the second layer gains importance.
The above embodiment similarly applies for deposition processes, in which the signal from an underlying layer is being reduced in the course of deposition, or the signal from the deposited layer is being increased.
As all methods described in this text, the method can be applied in in-situ but also ex-situ.
For example, the semiconductor substrate has a top first layer and a second layer beneath the first layer, the two layers having a different refractive index. When the top first layer has been etched away or partially been etched away, the X-rays are reflected at least partially by the second layer, this leading to a different signal.
Accordingly, in this embodiment, X-ray reflection is used for measurement instead of X-ray fluorescence. However, measurement of X-ray reflection may be combined with measurement of X-ray fluorescence as described above. Further, in other embodiments, instead of X-rays, electromagnetic waves of other wavelengths may be used for reflection such us UV light.
In an embodiment of the method of
Accordingly, before material of the first layer is etched away, total reflection of the incident X-Rays occurs at this material, and when material of the first layer has been etched away, the X-Rays are incident on the material of the second layer where they do not experience total reflection. This corresponds to a drop in reflected intensity which can be associated with an end point of the etch.
The method of
This embodiment will be better understood in the context of the examples of
Grazing angle θC indicates the angle of total refraction. X-ray X1 irradiated with that angle on the boundary 7 runs parallel to the boundary 7 and is not refracted into material with refractive index n2. All X-rays with an angle of incidence smaller than the critical angle of incidence θc, such as X-ray X2 with angle of incidence β, are totally reflected at boundary 7.
According to
Accordingly, incident X-rays are totally reflected as long as the second layer is covered by material of the first layer. Once the material of the first layer has been etched away, the prerequisites for total reflection are not present anymore such that total reflection is stopped in those areas in which the material of the first layer has been removed. This corresponds to a drop in reflected intensity, which may be sharp. This drop in reflected intensity is measured by the X-ray detection device 4 (see
Accordingly, as long as there is material A on the surface, total reflection occurs. When material A is removed, e.g. by plasma etching, the reflected intensity will drop down significantly, because the radiation will now enter material B where no total reflection happens. The corresponding signal indicative of the reflected X-rays will thus experience a change as well. In particular, such signal may experience a sharp (non-gradual) reduction or drop-off that can be associated with an end point of the etching process.
The direction of the incident X-rays is parallel to the lines 231a and spaces 231b, as indicated by arrows X. Before the material A of layer 231 has been etched away in the spaces 231b, total reflection in these areas occurred. After the spaces 231b have been etched, incident X-rays are not further totally reflected in these areas but will at least partly enter material B of layer 232, this corresponding with a change in the reflected intensity which can be evaluated to identify the endpoint of the etching process.
Again, there is provided a top layer 241, an intermediate layer 242 and a bottom layer 243. The top layer 241 includes lines 241a which comprise material B. At the sides of the lines, spacers 242b of material A are formed. Between the lines 241a and the spacers 241b spaces 242c are present. The intermediate layer 242 comprises material C and the bottom layer 243 comprises material D.
Again, in
Examples for the materials A, B, C and D in
The person skilled in the art will recognize that the embodiments described above are just examples and that other variations in the use of fluorescence and/or reflection may be implemented to measure a change in volume of a semiconductor substrate layer and/or to provide for endpoint detection of etching or depositing processes. For example, other parts of the electromagnetic spectrum than X-rays may be used for fluorescence and reflection such as ultraviolet (UV) light. Also, etching may be implemented by any etching apparatus and method such as plasma etching, ion beam etching and electron-induced reactive etching.
Claims
1. A method of manufacturing a semiconductor device, the method comprising:
- providing a semiconductor substrate; and
- producing at least one structured layer in the semiconductor substrate, such producing comprising: providing a process that changes volume of a portion of the semiconductor substrate, the portion of the semiconductor substrate comprising a region of a wafer, at least one layer of the semiconductor substrate or at least one layer deposited on the semiconductor substrate; and measuring a change in volume of the portion of the semiconductor substrate using fluorescence.
2. The method according to claim 1, wherein measuring the change in volume comprises providing at least one incidence X-Ray beam and measuring an intensity of fluorescence radiation such that the use of fluorescence includes the use of X-Ray fluorescence.
3. The method according to claim 2, wherein a penetration depth of the incidence X-Rays into the at least one layer is tuned by varying an angle of incidence of the incidence X-Ray beam.
4. The method according to claim 2, wherein the incidence X-Ray beam is provided at grazing incidence.
5. The method according to claim 1, wherein a change in volume is detected locally by measuring fluorescence of local areas of the portion of the semiconductor substrate penetrated by an incidence electromagnetic beam.
6. The method according to claim 1, wherein fluorescence is measured at least at a first time and a second time during the process that changes the volume of the at least one layer, and a change in volume is determined by the difference in fluorescence between the first and second times.
7. The method according to claim 1, wherein there is provided a top first layer the volume of which is changed during the process, and an underlying second layer the volume of which is not changed during the process, wherein the first layer comprises a first material having a fluorescence radiation with a first wavelength, and the second layer comprises a second material having a fluorescence radiation with a second wavelength, and wherein both layers are subjected to electromagnetic radiation.
8. The method according to claim 7, wherein the fluorescence signal of at least one of the first and second layers is evaluated to determine the end point of the change-in-volume process.
9. The method according to claim 7, wherein
- the change-in-volume process comprises an etching process;
- the fluorescence signal of the second layer is measured; and
- an end point is detected when the fluorescence signal of the second layer reaches a specified strength.
10. The method according to claim 9, wherein the reaching of a specified strength of the fluorescence signal of the second layer corresponds to a specific open area of the second layer produced by etching the first layer.
11. The method according to claim 9, wherein the etching process comprises a spacer etch in the course of a sublithographic patterning process and the reaching of a specified strength of the fluorescence signal of the second layer identifies an end point of the spacer etch in which a specific area of the second layer has been opened between the etched spacers.
12. The method according to claim 7, wherein
- the change in volume process is a deposition process;
- the fluorescence signal of the second layer is measured; and
- an end point is detected when the fluorescence signal of the second layer reaches a specified minimum.
13. The method according to claim 12, wherein the reaching of a specified minimum of the fluorescence signal of the second layer corresponds to a specific thickness of the first deposited layer.
14. The method according to claim 1, wherein the process which changes the volume of at least a layer of the semiconductor substrate or a layer added to the semiconductor substrate is an etching process or a deposition process.
15. A method of manufacturing a semiconductor device, the method comprising:
- providing a semiconductor substrate; and
- producing at least one structured layer in the semiconductor substrate, such producing comprising: providing a process that changes the volume of at least one layer of the semiconductor substrate or at least one layer deposited on the semiconductor substrate; and measuring a change in volume of such at least one layer using reflection of electromagnetic waves.
16. The method according to claim 15, wherein
- the substrate is irradiated with X-Rays;
- X-Rays reflected by the substrate are measured, and a signal is provided indicative of the intensity of the reflected X-rays; and
- the signal is evaluated to determine the change in volume of the at least one layer.
17. The method according to claim 16, wherein a decrease of the signal is associated with a reduction in thickness of the at least one layer and an increase of the signal is associated with a increase in thickness of the at least one layer.
18. The method according to claim 15, further comprising providing a top first layer of the semiconductor substrate and an second layer of the semiconductor substrate beneath the first layer, the two layers having a different refractive index.
19. A method of manufacturing a semiconductor device, the method comprising:
- providing a semiconductor substrate;
- providing a top first layer of the semiconductor substrate and a second layer of the semiconductor substrate beneath the first layer, the two layers having a different refractive index for X-Ray radiation; and
- etching the first layer of the semiconductor substrate, and during etching: irradiating the substrate with X-Rays; measuring the X-Rays reflected by the substrate, and providing a signal indicative of the reflected X-rays; determining a change in the signal; and associating an end point of the etching process with the change in the signal.
20. The method according to claim 19, wherein the signal experiences a drop-off that corresponds to a drop in the reflected X-Ray intensity, and wherein this drop-off is associated with an end point of the etching process.
21. The method according to claim 19, wherein
- the material of the first layer is chosen such that it has a first critical grazing angle of total reflection for X-Ray radiation;
- the material of the second layer is chosen such that it has a second critical grazing angle of total reflection for X-Ray radiation, the second critical angle being smaller than the first critical angle; and
- X-Rays are irradiated at the substrate at a grazing angle of incidence that is smaller than the first critical angle of total reflection for the material of the first layer and larger than the second critical angle of total reflection for the material of the second layer.
22. The method according to claim 21, wherein,
- before material of the first layer is etched away, total reflection of the incident X-Rays occurs at this material; and
- when material of the first layer is etched away, the X-Rays are incident on the material of the second layer where they do not experience total reflection such that there occurs a drop in reflected intensity.
23. The method according to claim 19, wherein etching includes etching of lines and spaces or a line etch and the X-Rays are irradiated in a direction parallel to the lines and spaces or lines.
24. A method of manufacturing a semiconductor device, the method comprising:
- providing a semiconductor substrate;
- providing a process which etches a top first layer of the semiconductor substrate or produces such layer, wherein a second layer of the semiconductor substrate is located beneath the first layer, wherein
- the materials of the first and second layers and the angle of incidence of the incident X-Rays are chosen such that total reflection of the incident X-Rays occurs or disappears when material of the first layer or at least parts of the first layer has been processed,
- the occurrence or disappearance of total reflection corresponding to an increase or drop in the intensity of the reflected X-Rays.
25. An apparatus for the manufacturing of semiconductor devices, the apparatus comprising:
- means for changing the volume of at least one layer of a semiconductor wafer or at least one layer deposited on the semiconductor wafer;
- an X-Ray radiation source;
- an X-Ray detection device detecting and measuring a signal indicative of the intensity of X-Rays reflected or emitted by fluorescence by the semiconductor wafer when irradiated with X-Rays by the X-Ray radiation source; and
- evaluating means for associating the signal with the change in volume process.
Type: Application
Filed: Mar 20, 2008
Publication Date: Sep 24, 2009
Inventors: Martin Haberjahn (Dresden), Sascha Dieter (Ottendorf-Okrilla), Andrea Graf (Dresden), Christoph Noelscher (Nuernberg), Dirk Manger (Dresden), Stephan Wege (Dresden)
Application Number: 12/051,932
International Classification: H01L 21/66 (20060101);